Fatigue performance of prosthetic screws used in dental implant restorations: Rolled versus cut threads

Abstract

Dental implants are widely used to replace missing teeth. 1 In direct-to-implant restorations, implant and abutment are joined by the preload obtained through the tightening torque applied to the prosthetic screw 2 as illustrated in Figure 1, providing the necessary structural integrity to the restoration. [3][4][5][6][7][8] The recommended torque value is provided by manufacturers based on different implant design factors. 9 Clinical studies suggest that the failure of implant restorations is often induced by fatigue because of the variable load conditions during their life span. [10][11][12] These failures typically occur in the prosthetic screw, with abutment or implant failures being less common. 13,14 The screw fracture is usually located at the first thread engaged with the implant. 15,16 Under given loading conditions, the number of cycles to fatigue failure depends on several parameters, including component dimensions, screw metric, material, manufacturing processes, and preload level. 17 Most prosthetic screws are made of pure or alloyed titanium, as these are less expensive than gold alloy screws while having excellent biocompatibility, corrosion resistance, machinability, and desirable physical and mechanical properties. 18,19 Two processes are widely used for screw thread manufacturing in industry: cutting and cold rolling. In thread cutting, material is removed from a cylindrical blank by machining, and in thread rolling, a matched set of dies displaces material of the manufacturing part to produce external threads on the

The Role of Thread Manufacturing Techniques on Dental Implant Abutment Screw Loosening

“…8). Similarly, the ndings of Armentia et al [25], revealed that surface roughness parameters for machined screws were consistently higher than those for thread rolled screws, although the SEM images in their study illustrated a contrasting scenario. The machined screws appeared to exhibit a lower surface roughness under SEM examination, a result that aligns seamlessly with the observations of this study.…”

“…As for the differences between the three manufacturing methods detailed in Table 3, while the thread angle should be consistent at 60 degrees across all screws, minor variations were observed in all methods. Similarly, Armentia et al [25] observed variations in the thread angle between machined and thread-rolled prosthetic screws. The variation in angle measurements can be attributed to defects caused by the roughness of the thread's side surfaces (Fig.…”

“…In restorations that attach directly to the implant, the implant and abutment are connected through the preload achieved by the tightening torque applied to the prosthetic screw [25,26], providing the essential structural integrity to the restoration [27][28][29]. The recommended torque value is provided by manufacturers based on various factors related to the design of the implant [9].…”

“…The researchers relied on mean torque results to compare the implant designs. In another study, Armentia et al [25] examined the impact of dental implant prosthetic screws on fatigue performance. The authors produced both thread-rolled and cut (machined) screws.…”

“…Screw thread manufacturing in the industry primarily relies on two processes: machining (cutting) and thread rolling [25]. In machining, equipment such as a CNC lathe precisely removes material from a workpiece to create the desired thread shape.…”